Plasma processes occur, for example, in plasma treatment and coating devices. Plasma can furthermore be used in etching or ashing processes. A very common plasma process is sputtering, in which accelerated ions from the plasma remove atoms from a target, and the atoms are then deposited on a substrate. For depositing compounds, such as, e.g., Al2O3, on the substrate, one often adds reactive gases when sputtering. This type of sputtering is called reactive sputtering.
In reactive sputtering, insulating layers also can be formed on the target. The ions that are accelerated onto the target can charge such insulating layers. If the field strength of an insulating layer that has been charged in this manner exceeds the breakdown field strength, arc discharges or arcs are formed. Arcs can be short-lived and self-extinguishing (such arcs can be referred to as short or micro arcs), or arcs can endure for a long time and have very high energy (such arcs can be referred to as hard arcs). Short arcs for the most part cause only a very small amount of damage and can be allowed to occur for many processes (e.g., glass coating processes). Hard arcs can lead to the destruction of the target and to imperfections on the substrate. Therefore, hard arcs can be suppressed by appropriate countermeasures.
For example, when a hard arc occurs, the current supplied by the plasma power supply can be briefly interrupted to prevent more severe damage to the sputtering system. Alternatively, the voltage applied to the plasma chamber can also be short-circuited or reversed in polarity. To initiate the above cited measures for the suppression of arc discharges, devices for the detection of an arc discharge or an arc and for the extinction of arc discharges are necessary when supplying power to the plasma processes. Such devices often form an integral part of the plasma power supply.
Because an interruption of the plasma power supply or a reversal in polarity of the same negatively affects the performance of the plasma process, and because short arcs are self-extinguishing, it is customary not to initiate countermeasure in response to detecting only short arcs.
WO 2006/014212 A2 discloses a method for the detection and treatment of arc discharges, in which the flow of power in a plasma from a power supply is interrupted for a pre-set period of time and then restored. If subsequently an arc discharge is again detected, the flow of power is once again interrupted.